Torrential downpours ahead
Heavy rain forecast for most of the North Island today and tomorrow is expected to hit hardest in some east coast areas.
A "burst of very heavy rain" was expected for Coromandel Peninsula, Bay of Plenty and northern Gisborne from tomorrow afternoon through to Thursday morning, MetService said.
Rainfall intensities during thunderstorms could reach up to 40mm an hour on the Coromandel and Bay of Plenty.
Intensities could be up to 30mm an hour in northern Gisborne.
This afternoon and evening there was a high risk of scattered thunderstorms over central parts of the North Island, with one or two possibly severe, producing localised downpours of up to 40mm an hour, MetService said.
"Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow river valleys, and may also lead to slips."
There was a moderate risk thunderstorms could extend to Northland.
The rain was being brought by a complex trough of low pressure which was moving slowly across the country during the next couple of days, MetService said.
A moist easterly flow was strengthening over central New Zealand today, while an unstable northerly flow covered northern areas.
Rain could also be heavy today and tomorrow about Waitomo, Taranaki, Taumarunui, Taihape, Taupo, Wairarapa, Wellington, as well as extending into eastern Marlborough and the Marlborough Sounds at the top of the South Island.
Rain could be heavy at times in Northland and Auckland tomorrow.
MetService severe weather forecaster Oliver Druce said the rain would be welcomed as it had been dry for much of the North Island and parts of the South Island.
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